Some prior art planters can control seed density within a given row of planted seeds. Deviation of plants from ideal row spacing can be associated with human error in manual driving of planters or machine error in automated guidance systems, such as position drift in satellite navigation receivers without real-time kinematic reference base stations or without real-time precise correction signals. Sometimes, actual crop yields are reduced from potential crop yields because of the planter's inaccuracies in the application of seeds or problematic adherence to prescriptions (e.g., zone-based prescriptions of corresponding the density, rate, or (row) spacing of seeds) from experienced farmers, agronomists or horticultural experts. Further, the grower or operator of the planter may tend to compensate for inaccuracies in planting by over-seeding or applying seeds with extra seed density that can reduce profit margins for growers (e.g., by requiring corresponding increased inputs of fertilizer and insecticide). Thus, there is a need for a planter with adjustable row units to provide appropriate or targeted level of seeds to soil or within corresponding zones within a field, such that plant or seed row spacing can be dynamically adjusted in the field.